Elevator systems include a variety of devices for providing control over movement of the elevator car. Elevator governors for protecting against over speed conditions are well known. Most elevator governors include a tripping mechanism located near the top of the hoistway. A governor rope extends along the length of the hoistway wrapping around a governor sheave associated with the tripping mechanism and an idler sheave associated with a tension weight near an opposite end of the hoistway. The elevator car is connected with the rope so that the rope moves as the elevator car moves. If the elevator car moves at a speed that is higher than desired, the speed of rotation of the governor sheave activates the tripping mechanism.
Governors in elevators systems are used for two purposes. One use of an elevator governor is for activating or dropping the machine brake and interrupting power to the machine motor in the event of an over speed condition. The other use is for activating elevator safeties that engage the guide rails, for example, in the event of a further over speed condition. Given that the governor reaction to each over speed condition is not independent, it is difficult to achieve specific control over the speed at which the governor performs both functions. Additionally, relying upon a single governor tripping mechanism for both functions introduces additional challenges when satisfying some codes for low speed elevators.